Methods for Differentiation and Quantitation of Creatine Kinase Isoenzymes

Creatine kinase (CK, adenosine triphosphate: creatine-N-phosphotransferase, EC 2.7.3.2) reversibly catalyses the phosphorylation of creatine by adenosine triphosphate (ATP) with formation of phosphocreatine and adenosine diphosphate (ADP)[433,449]: $$Creatine + ATP\overset {CK} \leftrightarrows Phosphocreatine + ADP$$ The optimum pH for the so called reverse reaction is 6.8, while the optimum pH for the forward reaction is 9.0. Because of the higher turnover rate in the reverse direction the reaction of phosphocreatine with ADP is two to six times faster depending on the conditions.